I think you're ignoring the on-use for the dreadguard relic. With the extra 350 power up 1/4 of the time, you have an average of 134 power from the DG relic. The WH relic gives a constant 113 power. Both of these are better than 66 WP and 27 crit.
Does the WH have a cooldown? If so I still fail to see it then, because the relics are on the same cooldown right? If not, then that totally makes sense..
I never actually looked at the WH relic..hmm gonna go look at it now. How long does it take to get? and how many WZs, I really hate PvP, but if it helps get me a bit more out of my healz, I will make the sacrifice